Abstract: It has been shown early by the authors that the spanwise mixing is caused by turbulent diffusion and different kinds of three dimensional flow effects.This paper introduces a computer program based on this theory. A new kind of rotary enthalpy has been defined and its related equation has been derived to simplify the present problem. The details for modeling all the unknown correlation mixing terms involved in the computations and the numerical scheme have been also presented. The results obtained agree well with the experiments for five compressors. The results also show some improvement over the previous theories.